SYSCTL.CONF(5) File Formats Manual SYSCTL.CONF(5)

# [NAME](#NAME)

sysctl.conf - Linux kernel configuration parameters

# [DESCRIPTION](#DESCRIPTION)

**sysctl.conf** is a set of configuration files that contain Linux kernel configuration parameters to be read and set by [**sysctl**(8)](/man/os/procps/sysctl.8).

This man page describes the configuration files for *procps* **sysctl**. If you are using [**systemd-sysctl**(8)](/man/os/procps/systemd-sysctl.8), refer to [**sysctl.d**(5)](/man/os/procps/sysctl.d.5) and note that it won't use the file */etc/sysctl.conf*.

## [Configuration Format](#Configuration_Format)

Each line of a file read by *procps* **sysctl** describes a kernel parameter in the following format.

```
token = value
```

There is no need to use quotation marks for *value*, even if the value is a list of items.

Blank lines and lines that start with “**#**” or “**;**” are ignored.

If a line begins with a single “**-**”, a failing attempt to set the value is ignored.

# [FILES](#FILES)

*procps* **sysctl**, when run with the **--system** option, reads files from directories in the order shown below.

*/etc/sysctl.d/*\**.conf*

*/run/sysctl.d/*\**.conf*

*/usr/local/lib/sysctl.d/*\**.conf*

*/usr/lib/sysctl.d/*\**.conf*

*/lib/sysctl.d/*\**.conf*

Finally, *procps* **sysctl** reads */etc/sysctl.conf*. This file is not used by **systemd-sysctl**, which means that some kernel parameters are not set depending on the implementation of **sysctl** that is installed.

# [BUGS](#BUGS)

The maximum supported length of *value* is 4096 characters due to a limitation on */proc* entry length in the Linux kernel.

# [EXAMPLES](#EXAMPLES)

```
#
#
kernel.domainname = example.com
; A value containing a space is written to the sysctl.
kernel.modprobe = /sbin/mod probe
# A list of items for the value
net.ipv4.ip_local_reserved_ports=8080,9148
```

# [SEE ALSO](#SEE_ALSO)

[**sysctl.d**(5)](/man/os/procps/sysctl.d.5), [**sysctl**(8)](/man/os/procps/sysctl.8), [**systemd-sysctl**(8)](/man/os/procps/systemd-sysctl.8)

2025-05-29 procps-ng

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Document: sysctl.conf(5) from procps 4.0.7-r2 (Chainguard OS)
Source: https://downloads.sourceforge.net/project/procps-ng/Production/procps-ng-4.0.7.tar.xz